This invention relates to dispensing of controlled amounts of liquid, and particularly relates to dispensing of liquid lubricants. It has special value for dispensing controlled quantities of suspension type, low viscosity lubricants.
One of the most effective lubricants marketed in recent years is the suspension type wherein a solid particulate lubricant such as molybdenum disulfide is suspended in a liquid carrier, preferably a low viscosity volatile organic liquid, e.g. "Dri-Slide" brand lubricant marketed by Dri-Slide, Inc. of Fremont, Mich. Such lubricants are so effective and so freely dispensible that over-use is an ever present tendency. In many applications, over-use results only in waste of lubricant. However, in some applications, over-use can result in lubricant flowing or dripping onto other than the intended equipment. As an example, it is a common practice to apply suspended type lubricants to conveyor wheels and chains. In fact, where the conveyor passes through pickling zones, paint spray zones, high heat zones as in ovens, or other conditions tending to destroy the lubricant and/or disrupt the bearing surfaces, the common practice is to lubricate the conveyor components at every recirculating pass. If excess lubricant is applied, it tends to flow or drip onto the goods supported by the conveyor. This can be a nuisance or even intolerable, as where it drips on white goods about to undergo further treatment.
Consequently, efforts have been expended to controllably dispense selected qualtities of lubricant, as through valved ejectors wherein the valve opened for a fraction of a second, at intervals, as with passage of conveyor components to be lubricated. It was soon learned however that lubricants, particularly of the suspension-type, are not readily controllably dispensed. Specifically, it was discovered that opening of the dispensing valve for a controlled time did not necessarily determine the timing, or the amount, or the character of the lubricant ejected. The lubricant did not seem to eject very forcefully unless high air pressure forces were used, and tended to be nonuniform in composition, usually being too high in carrier and too low in particulate. Also, the lubricant tended to continue dispensing in dribble or dripping fashion after the valve was closed and the conveyor component had passed. Often it separated into the particulate and carrier components in the valve and dispensing tubes leading from the valve, tending to plug the system. These results occurred even though the system was very technically sophisticated and expensive.
Upon realizing these factors, a great many experimental structures and combinations were tried in efforts to achieve controlled dispensing.